Track and field is a sport in which athletes compete in running, jumping, and throwing events. In an event known as the pole vault, an athlete uses a pole to jump over a cross bar. The pole vault originated in Europe where men used a wooden pole to cross over canals filled with water. By the late 1800s, the pole vault had been added as an event at track and field competitions. The early pole vaulters used a bamboo pole with a sharp point on the tip end and competed on a grassy surface. In the first modern Olympics in 1896, the winning vault was a height of ten and one-half feet (about 3.2 meters). In the following century, techniques and equipment improved so dramatically that the current record is over twenty feet (over 6.1 meters). One of the biggest improvements in equipment was a change to poles made of fiberglass.
Fiberglass poles are relatively light in weight. They also have the ability to bend a substantial amount as the vaulter plants the end of the pole into a box and then to straighten out to propel the athlete over the cross bar. In terms of physics, the vaulting pole converts the kinetic energy of the vaulter into potential energy that can be used to overcome the force of gravity. The kinetic energy of the vaulter is equal to one-half of his mass times his velocity squared. To achieve the same optimal amount of bend, the pole used by a heavy vaulter must be stiffer than the pole used by a light vaulter. Accordingly, vaulting poles are manufactured for specific weight classes. If a vaulter uses a pole adapted for a heavier vaulter, the pole will not bend enough, and if a vaulter uses a pole adapted for a lighter vaulter, the pole will bend too much. In either case, the vaulter will not be able to achieve the maximum height.
There is no limit to the length of the pole. The best male vaulters use a pole that is about seventeen feet (about 5.2 meters) long while high school girls may use a pole that is only about twelve feet long (about 3.7 meters). Fiberglass poles of this length typically weigh about two to seven pounds (about one to three kilograms). The weight of the pole has an effect on the speed the vaulter can achieve before planting the pole. As the pole becomes lighter, the vaulter can run faster. And, because the height of the vault is related to the kinetic energy generated by the vaulter and because the kinetic energy is related to the velocity squared, any decrease in the weight of the pole is highly desirable.
Fiberglass poles are manufactured by first wrapping multiple layers of epoxy resin impregnated fiberglass thread, tapes, cloths, or sheets around a metal mandrel. The terms “thread,” “tape,” “cloth,” and “sheet” are used arbitrarily in the industry depending on the width of the material. The glass fibers in the material may run in only one direction or they may be woven to run in two directions, perpendicular to each other. The direction in which the fibers run relative to the longitudinal axis of the pole determine the properties imparted to the pole. Fibers that run lengthwise (parallel to the longitudinal axis of the pole) provide column load bearing strength to the finished pole. Fibers that run radially (perpendicular to the longitudinal axis of the pole) provide hoop strength to the finished pole. Fibers that run at an angle between parallel and perpendicular provide both column load bearing strength and hoop strength. Fibers that run radially or at an angle, i.e., not parallel, are referred to herein as running transverse to the longitudinal axis.
After the layers of material are wrapped onto the mandrel, the pole is heated under pressure to cure (harden) the resin. The pole is then cooled and the mandrel removed. The pole is then cut to the desired length, caps are placed on the ends, and labels or the like is applied to the exterior of the pole. The manufacture of a specific fiberglass vaulting pole is described in detail in Jenks, U.S. Pat. No. 3,969,557, issued Jul. 13, 1976, which is incorporated by reference. The Jenks pole contains at least three layers of fiberglass tapes and cloth—the first (inner) layer is a helical-wrapped fiberglass tape, the second layer is a fiberglass cloth body piece, and the third layer is another helical-wrapped fiberglass tape. An optional fourth layer is a fiberglass trapezoidal sail piece.
In the late 1980s, straight run carbon fiber tapes and sheets became commercially available. As the name implies, the carbon fibers in these tapes and sheets run parallel to each other. Straight run carbon fiber tapes and sheets have substantial strength in only the direction of the fibers. As a result, they have been used as the helical tape and in straight body pieces where only one-dimensional strength is needed. Vaulting poles containing straight run carbon fibers typically weigh about ten percent less than a comparable pole made completely of fiberglass.
In the pursuit of even higher vaults, a demand exists for a vaulting pole that is even lighter in weight than fiberglass and straight run carbon fiber poles, but is similar or superior in other properties.